Why are posters saying taxing won't work?
Tobacco is a clear case study. It took a long time and also tons of public health messages, but saying its not effective is naive.
You're saying usage decreased because of public health message, ie eduction, not taxation. You honestly think people stopped buying cigarettes because they became too expensive? I'd say saving money is a convenient benefit of quitting, not the cause of. It's about health not money.
Addicts stop buying something when they are out of money, and then they find a way to get money so they can buy more.